Gas filled electric lamp



Oct. 29, 1935. F. ROTHER GAS FILLED ELECTRIC LAMP Filed Jan. 16, 1935 /nvento/:

Patented Oct. 29, 1935 UNITED STATES PATENT OFFICE GAS FILLED ELECTRIC LAMP Franz Rother, Paris, France, assignor to Rodalite Company, Inc., New York, N. Y., a corporation of New York 5 Claims.

The present invention relates to improvements in gaseous discharge lamps. Heretofore one type of lamp of this kind had a separately heated electrode which yielded a high electron emission and a low cathode drop, which characteristics could be still further improved by oxide coatings of the electrodes. These lamps could be operated at the usual low line voltages and yielded a strong gas discharge with a corresponding brilliant light from the excited gases. With certain types of such lamps which contain mercury and another gas the entire volume of the tube is filled with mercury light, while the heated electrodes are enveloped by a light of another color. However, these lamps are inefiicient and complicated because they require a special heating circuit for the heated electrodes.

Lamps have been constructed wherein an electrically excited gas is the source of light and which can be started and operated at the usual line voltages of 110 and 220 volts. This is, however, only possible if the gas pressure is such that a negative glow discharge of a few mm. depth envelopes the electrodes. This envelope of negative glow discharge represents the only light source, hence the size of the light source depends largely upon the size of the electrodes. These lamps called glow-lamps have electrodes which may have the shape of a hemisphere or of a letter. In the latter case each lamp may contain only one letter. For operation at the usual line voltages the lamps require a ballast resistance and have a relatively very low light emission. Their gas content consists of an inert gas or a mixture of such gases, the pressure of which is usually above 5 mm. Hg. The color of light from such lamps which contain gas mixtures is a mixture of the color of the individual gases.

In my copending application Serial No. 651,992, filed January 16, 1933, I have disclosed how it is possible in gas discharge devices containing a mixture of gases, to cause an emission of light of one color near the electrodes while light of another color is emitted by the gas in the space between the electrodes. This is accomplished by a regulating the partial pressures of the gases in the device and by suitable arrangement of form and size of the electrodes and of their position in the tube.

The present invention employs the above principle and by suitably shaping the electrodes and locating them relative to each other, novel lightlng efiects are produced due to the distribution or pattern of the two light components aforementioned.

The present invention has for its object to provide a glow discharge lamp which has a high efficiency.

Another object is to provide a glow discharge lamp which requires no external heating circuit 5 for the electrodes.

Another object is to provide a glow discharge lamp which exhibits two distinctly colored lights.

Another object is to provide a lamp in which the electrodes are shaped as letters or figures 10 which, when the lamp is energized, exhibit a color, which difiers from that of the light which fills the rest of the lamp.

To attain the above objects, I provide a lamp with suitably shaped electrodes and, in accord- 15 ance with my aforementioned application, fill it after evacuation with at least two components of gases or mixtures of gases or mixtures of gases and vapors, one component having a partial pressure above 6 mm. Hg. and the other compo- 0 nent having a partial pressure below 6 mm. Hg.

The accompanying drawing illustrates one embodiment of my invention. In the drawing,

Figure 1 illustrates a longitudinal section of a lamp, embodying one form of my invention.

Figs. 2 and 3 are enlarged cross sections through the electrodes of the lamp illustrated in Fig. 1.

Referring to the drawing, a glass bulb I is provided with two parallel wire electrodes 2 and 3. 30 At their one end the electrodes may be spaced apart by an insulating bridge 4 of glass or other suitable material. The other end of the electrodes 2 and 3 are connected to the screw shell 5 and center terminal 6 respectively of a con- 35 ventional lamp socket "l. The bulb is filled with two gases 8 and 9. Over the greater part of their length the electrodes are spaced apart a distance of about 2 mm. or less, while they are separated a greater distance at both ends.

The gas component 8 which hereafter will be called the protective component, has a partial pressure of over 6 mm. and preferably of 10 to 30 mm., while the component 9, which will be called the principal component has a partial 4!! pressure of less than 6 mm., preferably of 2 to 4 mm.

If the lamp is energized, the electrodes 2 and 3 are completely enveloped by a glow or light 8 which emanates from the protective component and which has a depth of about 1.5 mm., while the remainder of the space in the bulb is filled with a light 9 which emanates from the principal component. The light from the principal component does appear not only in the space between 56 the electrodes, but it permeates the entire inside space of the bulb.

If the distance of the-electrodes is sufilciently great, the light from the protective components surrounds the electrodes individually as indicated in Fig. 2, while for smaller distances of the electrodes the two envelopes, due to electrical repulsion of the ions between the electrodes, merge into one as indicated in Fig. 3.

The light effect of the protective component appears on both electrodes only with alternating current. In case of direct current it appears only on one electrode.

A lamp in accordance with my invention is externally characterized by the fact that the one gas component of higher pressure emits light only closely adjacent to the electrodes, and forms an envelope the shape-of which closely resembles that 01' the electrodes. The light is extraordinarily intense and brilliant.

The lamp may be fllled with gases or vapors or other gas having a partial pressure of less than Furthermore, an inert gas, that is, one of the gases of the first group of the periodic system of the elements of proper pressure may be used for the principal component and another gas for the supplemental component.

The protective and the principal component may also consist of an inert or of a common gasor of a mixture of inert gases only or of common gases only or finally of inert and common gases. In each case a metal vapor may be added. It is to be understood, however, that the respective gases of the mixture of each component must all have substantially the same partial pressure.

The described arrangement makes possible the construction of a gas discharge lamp without external heating circuit for the electrodes which lights with two dlil'erent colors. If such a lamp is provided with a frosted bulb, the light appears to the eye in the mixed color of the two components.

The relatively high pressure of the protective component acts to prevent the spattering of the electrodes which is observed with lamps having a filling of only a single gas of less than 6 mm. pressure. This spattering which greatly reduces the life of a lamp is obviated by the diflerentpressures of the two gas components. The protective component prevents the disintegration of the electrodes even when the current density of the lamp is so high that the electrodes are brought to red .heat by the ion bombardment from the principal gas. The heat generated thereby incremes the pressure of the protective component and this, in

turn, increases the protective eflect.

In certain cases the pressure of the protective gas component may be raised to 1 atmosphere or more. Under these conditions, the protective component does not usualy emit any more light high current density that the ion bombardment from the principal component raises the electrodes to red heat temperature.

The aforedescribed novelty is especially important for gases such as helium which hereto- 5 forerequired very large electrode surfaces to realize a reasonable life of the lamp. If one adds to helium of less than 6 mm. partial pressure a protective gas of considerably higher pressure such lamps can be constructed with heretofore unknown life.

The shape of the electrodes is not limited to the form shown in the drawing. They may be given the form of letters or other flgures'or objects which then appear in a color diiferent from that 15 of the intervening'spaee. Even though both electrodes of a lamp have the shape of letters, figures or the like, the lamp starts at the usual line voltage. The closely spaced electrodes shown in the drawing may have any desired length without 2 eifecting the starting and operation of the lamp at the usual line voltages. For instance, one electrode may have the form of a horizontal ring and the other may be a wire in the axis of the ring and terminating in its center or near thereto. In this case the ring and the wire are closely surrounded by the protective component, whfle the principal component occupies the space between the ring and the point of the wire.

The electrodes may consist of a radio-active metal or of an alloy containing a radio-active substance such as molybdenum-thorium alloy, or

they may consist of a sealing-in metal such as nichrome or nickel-iron. Finally the electrodes may consist of a core metal having a coating of another metal of a lower group and the same or a higher order than the base metal in the periodic system of elements.

The lamps may be designed for and operated with either direct or alternating current. In the 40 latter case, of course, the roles of cathode and anode are reversed every half cycle of the current.

It will be understood that wherever in the following claims I use the term gas components, such term may define a single gas or a mixture of two or more gases or a mixture of a gas or gases and metal vapor, all gases or vapor of the respective component having substantially the same partial pressure.

What I claim as new and desire to secure by, Letters Patent is:

1. A cold cathode electric gas discharge lamp comprising, in combination, a transparent envelope, at least two gas components, each of which when excited radiates a light of a distinct color, one of said gas components having a partial pressure of less than 6 mm. Hg and another of said components having a partial pressure of more than 6 mm. Hg, a cathode and an anode, said cathode and anode being arranged to cause the so light emittedthrough said envelope by said other component and surrounding said cathode to be disposed so as to form a given pattern which is surrounded by light of another color, emitted tlrilrlgugh said envelope by said one component o 2. A cold cathode alternating current gas discharge lamp comprising, in combination, a transparent envelope, at least two gas components, each of which when excited radiates a light of a distinct color, one of said gas components having apartialpressureoflessthanGmmHgand another of said components having a partial pressure of more than 6 mm. Hg, two electrodes so said envelope by said other component and surrounding said electrodes to be disposed so as to form a given pattern which is surrounded by light of another color, emitted through said envelope by said one component only.

3. A cold cathode alternating current gas discharge lamp comprising, in combination, a transparent envelope, at least two gas components, each of which when excited radiates a light of a distinct color, one of said gas components having a partial pressure of less than 6 mm. Hg and another of said components having a partial pressure of more than 6 mm. Hg, two electrodes so arranged that the light emitted through said envelope by said other component surrounds both electrodes in a single envelope which is disposed in a given pattern which is surrounded by light of another color, emitted through said envelope by said one component only. I

4. A cold cathode alternating current gas discharge lamp comprising, in combination, a transparent envelope, at least two gas components, each of which when excited radiates a light of a distinct color, one of said gas components having a partial pressure of less than 6 mm. Hg and another of said components having a partial pressure of more than 6 mm. Hg, two electrodes each arranged so as to cause the light emitted through said envelope by said other component and surrounding each electrode to form a given pattern which is surrounded by light of another color, emitted through said envelope by said one component only.

5. A cold cathode alternating current gas discharge lamp comprising, in combination, a transparent envelope, at least two gas components, each of which when excited radiates a light of a distinct color, one of said gas components having a partial pressure of less than 6 mm. Hg and another of said components having a partial pressure of more than 6 mm. Hg, two electrodes consisting of parallel wires spaced apart such a distance as to cause the light emitted through said envelope by said other component and surrounding said electrodes to form a given pattern which is surrounded by light of another color, emitted through said envelope by said one component only.

FRANZ ROTHER. 

